Question

Discuss the characteristics of 1NF, 2NF, and 3NF. As part of your discussion, you should describe how decomposition is used as part of the process to normalize a database schema.

Answer 1

The characteristics of 1NF, 2NF, and 3NF are as follows:

1. 1NF – According to the rule of 1NF, a table should hold only atomic values or single values. Some of the rule for 1NF are as follows:

• Each column in a table must have unique name.
• Each row can be uniquely identified (must have a primary key).
• Remove repeated groups.
• Order of rows does not matters.

2. 2NF – According to the rule of 2NF, a table must follow the rules given below:

• It must be in 1NF.
• No partial dependency - It should contains no non-prime attribute (attribute that is not a part of any candidate key) is dependent on the proper subset of any candidate key.

3. 3NF - According to the rule of 3NF, a table must follow the rules given below:

• It must be in 3NF.
• No Transitive Dependency – If X--->Y and Y--->Z is true, then X--->Z is a transitive dependency.
• For each functional dependency X--->Y, it must hold at least one of the condition, which is X must be super key and Y must be a prime attribute of table.

Decomposition is a process of breaking up of a relation into two or more relations so as to remove anomalies, redundancy, and inconsistencies of data in a relation.

Normalization is a process to organize the data so as to eliminate data redundancy and types of anomalies (insertion, deletion, update) by dividing the table into multiple tables. This dividing of the table into multiple tables is not possible without the decomposition. Therefore, decomposition is used as a part of normalization process of a database schema to minimize the data redundancy and anomalies.